Each of the following questions consists of six sentences of a passage. The first and sixth sentences are given as S1 and S6. The middle four sentences in each have been jumbled up and labeled as P, Q, R, and S. Find the proper sequence of the four sentences and mark your response accordingly.

S1: The Moon is Earth’s only natural satellite, the moon formed roughly 4.5 billion years ago.

P: About 0.2 billion years later, the South Pole- Aitken Basin was formed by a large impact.

Q: Between 4.1 and 3.8 billion years ago, was a period known as the heavy bombardment period.

R: During this period, the moon was hit with numerous impacts that left craters 3.1 to 1 billion years ago, mare volcanism took place.

S: During this time, the lava from under the crust broke through the surface and filled the craters with Mare.

S6: Also during this time, intermediate cratering was taking place, intermediate cratering was smaller asteroids and debris smashing into the moon, creating smaller craters in the surface of the mare.